This invention relates to electrical cords and plugs and more specifically to electrical cords and plugs that provide redundant grounding of a device to which the plug is connected.
Medical equipment is often used in wet or damp environments or in the presence of fluids which increases the hazard of electrocution or electrical shock from the device. Therefore, medical equipment is typically provided with cords and plugs for receipt into a receptacle providing a path to ground.
It is common practice to provide medical equipment and other equipment with a cord including a hot or live wire, a neutral wire, and a ground wire. These cords terminate in a three-prong plug having a live prong, a neutral prong, and a ground prong electrically connected to the live wire, neutral wire, and ground wire respectively. Electrical outlets in health care facilities typically include grounded receptacles for receipt of a three-prong plug. The receptacles include conductive paths that are connected to a live line terminating at the hot bus of the electrical supply, a neutral line terminating at the neutral bus of the electrical supply, and a ground line terminating at the ground bus of the electrical supply providing a path to ground for current. The ground wire and conductive path connected to the ground line form parts of a ground circuit. Damage to any part of the ground circuit, including the plug, receptacle, or cord subjects a patient to the possibility of electrical shock from the medical device.
Ground fault interrupter circuits are available which detect electrical surges caused by failure of grounding circuitry and interrupt the currents supplied to the live wires. However, in a medical environment, interruption of electrical power to the medical equipment can have catastrophic results precluding the use of ground fault interrupter circuits with many medical devices. Therefore, the preferred method of preventing electrical shock in medical devices is to provide for redundant grounding of the medical device. This method of reducing electrical shock hazards is discussed in Martucci, U.S. Pat. No. 4,025,139. Martucci discloses several configurations of power cords, plugs, and receptacles for providing redundant grounding of electrical devices. The devices disclosed in Martucci require replacement or modification of standard duplex receptacles typically present in a health care facilities.
Health care facilities would welcome an electrical cord and plug which provides for redundant grounding of medical devices and which could be used without replacement of, or modification of, hospital grade duplex receptacles currently present in health care facilities.
A power cord and plug in accordance with the present invention for use with a standard grounded duplex receptacle having two three-contact sockets includes a plug housing having a power prong, a neutral prong, a first ground prong, and a second ground prong, and four separate conductors connected at one end to one of each of the power prong, neutral prong, first ground prong, and second ground prong. The power prong, neutral prong, and first ground prong are arranged to be received in the power contact, neutral contact, and ground contact of one of the two sockets present in the duplex receptacle while the second ground prong is received in the ground contact of second socket present in the duplex receptacle. A flexible boot extends from the plug housing and is configured to form a seal around the power prong, neutral prong, first ground prong, and second ground prong when the prongs are properly received in the duplex receptacle.
Features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of an illustrated embodiment exemplifying the best mode of carrying out the invention as presently perceived.